1. Field of the Invention
The invention relates to the manufacture and assembly of rims for cycles and, more particularly, to a rim using a sleeve connection and a method for manufacturing such rim. The invention further includes a wheel having such rim and a method of manufacturing such wheel.
2. Description of Background and Other Information
Rims, in particular cycle rims, such as bicycle rims, are manufactured from a shaped element made of aluminum or aluminum alloy that is bent to form the rim. In most cases, a cycle rim is connected to the hub by sets of spokes to form the cycle wheel. The shaped element used for a rim can be any of various types, but it is typically U-shaped, including a pair of upstanding lateral flanges, and side walls which sometimes include, or provide, braking surfaces against which brake pads apply braking pressure.
Currently available rims are conventionally manufactured, as known to those skilled in the art, from a shaped element having a predetermined length, which is bent, the two ends of which are joined and fixed together. The rigidity of the hoop thus made is naturally dependent upon the quality of the material used to make the initial shaped element, and particularly upon its strength, which results from a so-called drawing process, or from the extrusion of aluminum, e.g., through a die having the dimensions and the form of the shaped element to be made.
One of the particular problems in the construction of rims is the connection of the ends after the bending operation. There are different methods of connecting the ends of the shaped element, none of which is entirely satisfactory.
A widely known method involves butt-joining the two ends of the bent shaped element, and then flash welding them in the area of the junction line between the two ends. A welding seam results from this method, which must then be milled and brushed. These operations are difficult to carry out on rim profiles that are quite complex. For the machining, a milling cutter must move around the profile by following the welding seam. Generally, a different milling cutter is used to eliminate the bulges on the inner surfaces of the lateral flanges and at the rim bottom, on which the tire is to be mounted. These operations require the use of specific devices particularly adapted therefor. Such a method is therefore expensive and is in fact used by certain manufacturers to make “top of the line” rims only. Moreover, the mechanical characteristics of the rim can be affected due to the welding operation, which causes metal annealing in the welded area by locally reducing the strength therein.
Another method involves coupling the two ends using two pins that are laterally spaced apart, and which penetrate into lateral channels provided in the rim shaped element. To obtain good strength for the junction, the adjustment must be tight and the dimensional tolerances must be completely controlled. Moreover, the rim shaped elements obtained are heavier due to the material surplus for each channel made. In addition, this method raises problems related to drawing the rim shaped element, which is complex to carry out. The drawing speeds are therefore quite low to obtain the necessary geometric and dimensional precisions. It is also necessary to provide a pairing of the connection pins in order not to damage the channels and to control the tightening forces properly.
Another method involves a sleeve coupling of a hollow tube that is prestressed within the cross section of the rim profile. The shape of the tube substantially complements that of the inner cross section of the shaped element. It is obtained by drawing a usually aluminum-base light alloy. With this technique, it is difficult to properly control tolerances below 0.3 mm. The rim profile is made by drawing or by extrusion, and the tolerance control is therefore approximately the same. Thus, it is difficult to always achieve a good tightening of the sleeve in the rim, in view of the dispersion of the dimensional tolerances of the rim and of the sleeve. Another drawback is that the length of the tube is often greater than the length separating two successive openings provided in the rim for attaching the spokes. It is therefore necessary to drill bores in the tube, in the area of these openings. This operation is difficult to carry out for extremely profiled rims intended for use in competition. It is also quite expensive. Moreover, it is necessary to use longer eyelets in the sleeve opening locations to hold the spokes; which implies having to manage a greater number of part references in the manufacture of the rim, and therefore to incur additional cost.
U.S. Pat. No. 4,938,540-A relates to a rim and the manufacturing method thereof, which uses a pin connection. An adhesive is used inside the channels in which the pins are inserted to overcome a sealing problem.
French Patent Publication No. 2 733 459-A1 proposes to overcome the drawbacks of the prior art by providing the connection for a rim by means of a sleeve made of two expansible portions and by means of a screw. The screw causes a relative spacing apart of the portions. However, one of the drawbacks with this solution relates to the deformation of the rim profile. Indeed, the force applied radially to eliminate backlash, i.e., to compensate for play between the sleeve and the rim, can cause a local deformation of the transverse bridge and/or of the lower base wall of the rim, which is generally tapered. This deformation can affect the control of the tightening force as well as the mechanical strength characteristics of the rim. The sleeve is also made of two elements which are adapted to be spaced apart by means of a screw, which makes the rim more expensive to manufacture and not easy to assemble and tighten. Finally, the arrangement of the screw does not allow fitting a sleeve on a rim having a flattened or low profile because the two portions of the sleeve do not have sufficient rigidity and strength, and the sleeve is also weakened by the central space.